We examined whether long-term antihypertensive monotherapy with enalapril decreased clinical casual blood pressure (BP) as well as BP at work and during stress, and whether this angiotensin-converting enzyme (ACE) inhibitor had an adverse effect on the physiologic hemodynamic pattern during experimental mental stress. Seventeen male patients with hitherto untreated mild-to-moderate essential hypertension (mean age: 47 ± 8 years) had 24-hour BP monitored noninvasively with the Physioport system before and during treatment with enalapril (5–10 mg/day) for 6 months. They also had a mental stress test, physical exercise test, and the cold pressor test before and after therapy. After the diagnostic observation period, average clinical casual BP was 150 ± 12/102 ± 7 mg Hg. Average BP at work, stress BP during all types of stimulation in the laboratory, and clinical casual BP significantly decreased during monotherapy with enalapril. Neither the circadian rhythm nor the hemodynamic pattern during mental stress was significantly altered by enalapril. BP increases during emotional stress were not significantly attenuated by the ACE inhibitor. These results demonstrated that enalapril effectively lowers BP without altering the physiologic hemodynamic pattern during emotional stress.